Zelensky met military officials and handed out awards to Ukrainian servicemen, who have been holding back a fierce and months-long Russian campaign for the city.

To gain control of the city, Russia is believed to have relied on mercenaries, prison conscripts and newly mobilised soldiers to send waves of attacks against Ukrainian positions.

The brutal trench warfare and artillery battles around Bakhmut -- once known for its vineyards and cavernous salt mines -- have flattened large portions of the city and its surroundings.

"I'd like to wish there was light but the situation is so difficult that there is light and then there is no light. The main thing is that there light is inside," Zelensky said, according to local media, referring to systematic strikes that targeted Ukraine's electricity grid.

"Bakhmut is the eastern fortress of Ukraine," Deputy Defence Minister Ganna Malyar, who was also visiting Bakhmut, said in a statement on social media.

"Tomorrow is the winter equinox and the nights will get shorter. The darkest night will end with the dawn of our victory," she said.

The visit comes after Russian President Vladimir Putin said earlier Tuesday the situation in several territories of Ukraine that Moscow claims to have annexed but does not control militarily was "extremely difficult".

-'Extremely difficult'-

Putin in September announced the annexation of four regions in the east and south of Ukraine after Moscow's proxies held referendums there, denounced as a sham by Kyiv and the West.

His troops never fully controlled any of the territories and last month were forced to retreat from the regional capital of the southern Kherson region after a months-long Ukrainian counteroffensive.

"The situation in the Donetsk and Lugansk People's Republics, in the Kherson and Zaporizhzhia regions is extremely difficult," Putin told the Russian security services on their professional holiday.

Singling out those working in the "new regions of Russia", he added that "the people living there, the citizens of Russia, rely on you, on your protection".

And at an award ceremony in the Kremlin later Tuesday, the Russian leader handed decorations to the Moscow-installed leaders of the regions.

"Our country has repeatedly faced challenges and defended its sovereignty. Today, Russia is once again facing the same challenge," he said, referring to territories recaptured by Ukraine.

- Putin, Lukashenko meeting a 'dance' -

Putin's comments came one day after his first visit in several years to neighbouring Belarus for talks with strongman leader Alexander Lukashenko, who allowed Russian troops to use his country to launch their invasion of Ukraine in February.

Ukrainian military said after the visit that there was a growing threat of another potential attack from Belarusian territory but that its forces were taking steps to prepare.

"We closely monitor the weapons being transferred from Russia," said Sergiy Nayev, commander of Ukraine's joint forces.

"The level of the military threat is gradually increasing but we are also taking adequate measures."

The foreign ministry meanwhile dismissed the talks as political theatre, even though the leaders vowed deeper military cooperation during talks.

"The Putin and Lukashenko meeting is another dance they have performed... no critical decisions were made. Whatever happens, we are ready for any scenario," Ukraine's Foreign Minister Dmytro Kuleba said during an online briefing.

Putin denied plans to absorb Belarus during the visit Monday but the two ex-Soviet allies vowed closer military cooperation going forward.

The Ukrainian presidency meanwhile said that Russian attacks across Ukraine had left five people dead including three in the Donetsk region, where Bakhmut is located, and in the Kherson region.

The war has taken a significant toll on Ukraine's economy and the IMF said Monday it had approved an economic monitoring programme which could help Kyiv secure funding from donors, with the war-torn country needing more than $40 billion this year.